19G .MORPHOLOGY AND EVOLUTION
connected to the deep fascia of the leg. Between it and the subjacent gracilis lie the saphenous nerve and vessels.
The quadriceps extensor is composed of the same elements as in Man, but they are more fused. The rectus femoris has a single head of origin in the Gibbon, but in the other Apes there are two heads forming an arch over the upper border of the acetabulum. In the Chimpanzee the vastus externus arises from the antero-lateral aspect of the great trochanter and the back of the shaft of the femur to a point an inch above the external condyle, and a small slip arises from the upper end of the intertrochanteric line ; the vastus internus arises from the intertrochanteric line, except from its extreme upper end, and from the same extent of the shaft of the femur as the vastus externus ; the crureus arises from the upper two-thirds of the shaft of the femur between the vasti: and the tendon of the quadriceps is inserted into the upper border of the patella, the capsule of the joint on either side of it, the external condyle of the femur and the two condyles of the tibia; and the ligamentum patellae is inserted into the front of the upper end of the tibia. No subcrureus is present in the Chimpanzee.
The adductor muscles exhibit many specific and individual variations, as can be seen from the writings of Hepburn (83), Humphry (340), Gratiolet (330), Champneys t318), and Sonntag (399). In the Chimpanzee (fig. 36, A) the gracilis and adductor longus arise together from the inner end of Poupart's ligament, the entire length of the symphysis and the upper third of the descending ramus of the pubis. The adductor longus